Retaining wall structures that use horizontally-positioned soil inclusions to reinforce an earth mass in combination with a facing element are referred to as mechanically stabilized earth (MSE) structures. MSE structures can be used for various applications including retaining walls, bridge abutments, dams, seawalls, and dikes.
The basic MSE implementation is a repetitive process in which layers of backfill and horizontally-placed soil reinforcing elements are positioned one atop the other until a desired height of the earthen structure is achieved. Typically, grid-like steel mats or welded wire mesh are used as soil reinforcing elements. In some applications, the soil reinforcing elements consist of parallel, transversely-extending wires welded to parallel, longitudinally-extending wires. Backfill material and the soil reinforcing mats are combined and compacted sequentially to form a standing earthen formation or wall.
During construction of the MSE structure, the soil reinforcing elements can be successively coupled or otherwise attached to a substantially vertical wire wall, much like a wire mesh or wire gridworks. Coupling the soil reinforcing elements to the wire wall serves to maintain the shape of the earthen formation. MSE structures derive their strength and stability from the frictional and mechanical interaction between the backfill material and the soil reinforcement elements, resulting in a permanent and predictable load transfer from backfill to reinforcements.
In a two-stage MSE system a substantially vertical wall or facing is constructed a short distance from the earthen formation. The facing may be made of, for example, concrete or metal and attached in several locations to the earthen formation, most likely to the wire wall, by a variety of mechanisms. Via this attachment, outward movement and shifting of the facing is prevented. In operation, the facing not only serves as a decorative façade, but also prevents erosion at the face of the earthen formation.
Although there are several systems and methods of constructing two-stage MSE structures, it nonetheless remains desirable to find improved systems and methods offering less expensive alternatives and greater resistance to shear forces inherent in such structures.